Ventilation-perfusion inequality during normoxic and hypoxic exercise in the emu

2002 ◽  
Vol 93 (6) ◽  
pp. 1980-1986 ◽  
Author(s):  
P. M. Schmitt ◽  
F. L. Powell ◽  
S. R. Hopkins
Keyword(s):  
Cardiac Output ◽  
Standard Deviation ◽  
Treadmill Exercise ◽  
Hypoxic Condition ◽  
Avian Species ◽  
Inert Gas ◽  
Intrapulmonary Shunt ◽  
The Stability ◽  
Hypoxic Exercise

Many avian species exhibit an extraordinary ability to exercise under hypoxic condition compared with mammals, and more efficient pulmonary O2 transport has been hypothesized to contribute to this avian advantage. We studied six emus ( Dromaius novaehollandaie, 4–6 mo old, 25–40 kg) at rest and during treadmill exercise in normoxia and hypoxia (inspired O2 fraction ≈ 0.13). The multiple inert gas elimination technique was used to measure ventilation-perfusion (V˙/Q˙) distribution of the lung and calculate cardiac output and parabronchial ventilation. In both normoxia and hypoxia, exercise increased arterial Po 2 and decreased arterial Pco 2, reflecting hyperventilation, whereas pH remained unchanged. The V˙/Q˙ distribution was unimodal, with a log standard deviation of perfusion distribution = 0.60 ± 0.06 at rest; this did not change significantly with either exercise or hypoxia. Intrapulmonary shunt was <1% of the cardiac output in all conditions. CO2 elimination was enhanced by hypoxia and exercise, but O2 exchange was not affected by exercise in normoxia or hypoxia. The stability of V˙/Q˙ matching under conditions of hypoxia and exercise may be advantageous for birds flying at altitude.

Ventilation-perfusion relationships in the lung during head-out water immersion

1992 ◽  
Vol 72 (1) ◽  
pp. 64-72 ◽  
Author(s):  
T. Derion ◽  
H. J. Guy ◽  
K. Tsukimoto ◽  
W. Schaffartzik ◽  
R. Prediletto ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Standard Deviation ◽  
Minute Ventilation ◽  
Water Immersion ◽  
Inert Gas ◽  
Closing Volume ◽  
O2 Uptake ◽  
Tidal Breathing ◽  
Normal Males ◽  
Arterial Po2

Water immersion can cause airways closure during tidal breathing, and his may result in areas of low ventilation-perfusion (VA/Q) ratios (VA/Q less than or equal to 0.1) and/or shunt and, ultimately, hypoxemia. We studied this in 12 normal males: 6 young (Y; aged 20–29 yr) with closing volume (CV) less than expiratory reserve volume (ERV), and six older (O; aged 40–54 yr) with CV greater than ERV during seated head-out immersion. Arterial and expired inert gas concentrations and dye-dilution cardiac output (Q) were measured before and at 2, 5, 10, 15, and 20 min in 35 degrees C water. During immersion, Y showed increases in expired minute ventilation (VE; 8.3–10.3 l/min), Q (6.1–8.2 l/min), and arterial PO2 (PaO2; 91–98 Torr; P less than or equal to 0.05). However, O2 uptake (VO2), shunt, amount of low-VA/Q areas (% of Q), and the log standard deviation of the perfusion distribution (log SDQ) were unchanged. During immersion, O showed increases in shunt (0.6–1.8% of Q), VE (8.5–11.4 l/min), and VO2 (0.31–0.40 l/min) but showed no change in low-VA/Q areas, log SDQ, Q, or PaO2. Throughout, O showed more VA/Q inequality (greater log SDQ) than Y (O, 0.69 vs. Y, 0.47).(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism of exercise-induced hypoxemia in horses

1989 ◽  
Vol 66 (3) ◽  
pp. 1227-1233 ◽  
Author(s):  
P. D. Wagner ◽  
J. R. Gillespie ◽  
G. L. Landgren ◽  
M. R. Fedde ◽  
B. W. Jones ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Treadmill Exercise ◽  
Inert Gas ◽  
Diffusion Limitation ◽  
O2 Uptake ◽  
Heavy Exercise ◽  
Physiological Basis ◽  
Blood Temperature ◽  
Exercise Induced ◽  
Arterial Po2

Arterial hypoxemia has been reported in horses during heavy exercise, but its mechanism has not been determined. With the use of the multiple inert gas elimination technique, we studied five horses, each on two separate occasions, to determine the physiological basis of the hypoxemia that developed during horizontal treadmill exercise at speeds of 4, 10, 12, and 13–14 m/s. Mean, blood temperature-corrected, arterial PO2 fell from 89.4 Torr at rest to 80.7 and 72.1 Torr at 12 and 13–14 m/s, respectively, whereas corresponding PaCO2 values were 40.3, 40.3, and 39.2 Torr. Alveolar-arterial PO2 differences (AaDO2) thus increased from 11.4 Torr at rest to 24.9 and 30.7 Torr at 12 and 13–14 m/s. In 8 of the 10 studies there was no change in ventilation-perfusion (VA/Q) relationships with exercise (despite bronchoscopic evidence of airway bleeding in 3) and total shunt was always less than 1% of the cardiac output. Below 10 m/s, the AaDO2 was due only to VA/Q mismatch, but at higher speeds, diffusion limitation of O2 uptake was increasingly evident, accounting for 76% of the AaDO2 at 13–14 m/s. Most of the exercise-induced hypoxemia is thus the result of diffusion limitation with a smaller contribution from VA/Q inequality and essentially none from shunting.

scholarly journals On the Stability of a Stochastic Nonlinear Model of the Heart Beat Rate During a Treadmill Exercise

2020 ◽  
Vol 53 (2) ◽  
pp. 16457-16461
Author(s):  
Mohammad Mostafa Asheghan ◽  
Bahram Shafai ◽  
Joaquín Míguez
Keyword(s):  
Nonlinear Model ◽  
Treadmill Exercise ◽  
Heart Beat ◽  
Beat Rate ◽  
Heart Beat Rate ◽  
The Stability

scholarly journals Evaluation of inert gas rebreathing for determination of cardiac output: influence of age, gender and body size

2018 ◽  
Vol 42 (6) ◽  
pp. 834-844 ◽  
Author(s):  
Jessica E. Middlemiss ◽  
◽  
Alex Cocks ◽  
Kaido Paapstel ◽  
Kaisa M. Maki-Petaja ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Body Size ◽  
Inert Gas ◽  
Inert Gas Rebreathing

Estimation of ventilation-perfusion inequality by inert gas elimination without arterial sampling

1985 ◽  
Vol 59 (2) ◽  
pp. 376-383 ◽  
Author(s):  
P. D. Wagner ◽  
C. M. Smith ◽  
N. J. Davies ◽  
R. D. McEvoy ◽  
G. E. Gale
Keyword(s):  
Cardiac Output ◽  
Venous Blood ◽  
Inert Gas ◽  
Chronic Obstructive ◽  
Obstructive Pulmonary Disease ◽  
Arterial Access ◽  
Arterial Blood ◽  
Potential Applications ◽  
Clinical Interest ◽  
Mixed Venous

Estimation of ventilation-perfusion (VA/Q) inequality by the multiple inert gas elimination technique requires knowledge of arterial, mixed venous, and mixed expired concentrations of six gases. Until now, arterial concentrations have been directly measured and mixed venous levels either measured or calculated by mass balance if cardiac output was known. Because potential applications of the method involve measurements over several days, we wished to determine whether inert gas levels in peripheral venous blood ever reached those in arterial blood, thus providing an essentially noninvasive approach to measuring VA/Q mismatch that could be frequently repeated. In 10 outpatients with chronic obstructive pulmonary disease, we compared radial artery (Pa) and peripheral vein (Pven) levels of the six gases over a 90-min period of infusion of the gases into a contralateral forearm vein. We found Pven reached 90% of Pa by approximately 50 min and 95% of Pa by 90 min. More importantly, the coefficient of variation at 50 min was approximately 10% and at 90 min 5%, demonstrating acceptable intersubject agreement by 90 min. Since cardiac output is not available without arterial access, we also examined the consequences of assuming values for this variable in calculating mixed venous levels. We conclude that VA/Q features of considerable clinical interest can be reliably identified by this essentially noninvasive approach under resting conditions stable over a period of 1.5 h.

Effect of inspired CO2 on ventilation and perfusion heterogeneity in hyperventilated dogs

1993 ◽  
Vol 75 (3) ◽  
pp. 1306-1314 ◽  
Author(s):  
K. B. Domino ◽  
E. R. Swenson ◽  
N. L. Polissar ◽  
Y. Lu ◽  
B. L. Eisenstein ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Partial Pressure ◽  
Respiratory Rate ◽  
Dead Space ◽  
Pressure Difference ◽  
Inert Gas ◽  
Ventilation Distribution ◽  
Pentobarbital Sodium ◽  
Ventilation And Perfusion ◽  
Paco2 Level

We studied the effect of inspired CO2 on ventilation-perfusion (VA/Q) heterogeneity in dogs hyperventilated under two different tidal volume (VT) and respiratory rate conditions with the use of the multiple inert gas elimination technique. Dogs anesthetized with pentobarbital sodium were hyperventilated with an inspired fraction of O2 of 0.21 by using an increased VT (VT = 30 ml/kg at 18 breaths/min) or an increased respiratory rate (VT = 18 ml/kg at 35 breaths/min). The arterial CO2 tension (PaCO2) was varied to three levels (20, 35, and 52 Torr) by altering the inspired PCO2. The orders of type of ventilation and PaCO2 level were randomized. Compared with normocapnia, VA/Q heterogeneity was increased during hypocapnia induced by increased respiratory rate ventilation, which was indicated by an increase in dispersion indexes and arterial-alveolar inert gas partial pressure difference areas (P < 0.01). In contrast, VA/Q heterogeneity was not affected by hypocapnia when a large VT ventilation was used. Under the conditions of our study, hypercapnia did not result in statistically significant changes in VA/Q heterogeneity with either type of ventilation. Increased VT ventilation reduced dead space at all PaCO2 levels (P < 0.01) and reduced the log standard deviation of the ventilation distribution during normocapnia (P < 0.05) and hypocapnia (P < 0.01). We conclude that hypocapnia increased VA/Q heterogeneity when hyperventilation was achieved with a rapid respiratory rate. Therefore, a lack of improvement in VA/Q matching with inhaled CO2 may be associated with the use of a large VT. These data suggest that hypocapnic bronchoconstriction may be important in mediating hypocapnia-induced VA/Q inequality in dogs.

Inert gas rebreathing - helpful tool in the management of left ventricular assist device patients

Perfusion ◽  
2018 ◽  
Vol 33 (5) ◽  
pp. 335-338 ◽  
Author(s):  
Nils Reiss ◽  
Thomas Schmidt ◽  
Stephanie Mommertz ◽  
Christina Feldmann ◽  
Jan Dieter Schmitto
Keyword(s):  
Cardiac Output ◽  
Exercise Capacity ◽  
Left Ventricular ◽  
Inert Gas ◽  
Ventricular Assist Devices ◽  
Test Protocol ◽  
Ventricular Assist ◽  
Helpful Tool ◽  
Inert Gas Rebreathing ◽  
Left Ventricular Assist

In patients with left ventricular assist devices (LVAD), exercise capacity is a decisive factor regarding the quality of life. When evaluating exercise capacity, precise information about the total cardiac output generated is crucial. To date, complex measurements using a right-heart catheter were necessary in order to determine total cardiac output. The inert gas rebreathing method facilitates non-invasive, direct and valid measurement of total cardiac output as well as associated parameters, like the difference in arteriovenous oxygen saturation, both at rest and during exercise. It is the aim of this paper to focus on this conclusive method which is, despite its simplicity and low-risk reproducibility, rarely used within the framework of LVAD patient treatment at the present time. The test protocol used at our hospital is presented to facilitate the implementation of this helpful tool in other interested institutions.

Effect of test parameters on the stability of fabric shape retention indexes increase recovery testing

2021 ◽  
pp. 004051752110242
Author(s):  
Qianhui Tang ◽  
Lei Wang ◽  
Weidong Gao ◽  
Ruru Pan
Keyword(s):  
Standard Deviation ◽  
Sample Size ◽  
Orthogonal Test ◽  
Test Scheme ◽  
Optimal Test ◽  
Pressure Time ◽  
Test Parameters ◽  
Shape Retention ◽  
The Stability ◽  
Retention Indexes

Fabric shape retention is a crucial property that impacts the durability and usability of fabric and which needs a convenient and accurate evaluation method. In the previous research, the automated crease recovery testing method was used to obtain fabric crease recovery information and evaluate the property of shape retention. Based on the previous research, an orthogonal test method was adopted to investigate the effect of different test parameters on the stability of shape retention detection in this paper. First, three factors, that of sample size, pressure, and pressure time, and three different levels of each factor were determined by the L9(34) orthogonal test table. Next, the fabric shape retention indexes were detected by nine different test schemes, and the comprehensive score of shape retention index standard deviation was obtained as the evaluation criterion of the orthogonal test results. Finally, the optimal test scheme was determined by visual analysis and variance analysis. The results show that the sample size has a certain effect on the stability of shape retention indexes, while the pressure time and the pressure have no significant influence. The optimal test scheme is that the sample size is 30 cm × 30 cm, the pressure time is 60 s, and the pressure is 40 N. The test result measured by the optimal test parameters reveals excellent stability when the vertex angle standard deviation is 2.0°, the height standard deviation is 0.06 cm, and the shape retention area standard deviation is 0.16 cm2. This paper provides an experimental basis for improving the accuracy of fabric shape retention evaluation method.

EVALUATION OF IMPEDANCE CARDIAC OUTPUT IN CHILDREN

PEDIATRICS ◽  
1971 ◽  
Vol 47 (5) ◽  
pp. 870-879
Author(s):  
Zuhdi Lababidi ◽  
D. A. Ehmke ◽  
Robert E. Durnin ◽  
Paul E. Leaverton ◽  
Ronald M. Lauer
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Standard Deviation ◽  
Pulmonary Blood Flow ◽  
Impedance Measurement ◽  
Aortic Insufficiency ◽  
Mean Difference ◽  
Dye Dilution ◽  
Impedance Cardiograph ◽  
Indicator Dye

In 20 children without shunts or valvular insufficiency, duplicate dye dilution and impedance cardiac outputs (ICO) were carried out. The duplicate dye dilutions had a standard deviation 0.259 L/min/m2, while duplicate ICO had a standard deviation 0.192 L/min/m2 (F = 1.82, p &lt; 0.05). Of 53 sequential estimates, cardiac outputs measured by both indicator dye dilution and ICO had a 5.5% mean difference. In 21 subjects with left to right shunts, the ICO related well with pulmonary blood flow (r = 0.92) rather than systemic flow (r = 0.21). In 13 subjects with aortic insufficiency, sequential Fick and ICO had a 50% mean difference; the impedance measurement was found to be higher in every case. These data indicate that the impedance cardiograph can provide a noninvasive measure of cardiac output when there are no shunts or valvular insufficiencies. In subjects with left to right shunts the impedance cardiograph provides a measure of the pulmonary blood flow. When aortic insufficiency exists the impedance cardiograph is distorted such that it is consistently higher than Fick cardiac output.

Sign in / Sign up

Export Citation Format

Share Document